Uncertainty surrounded Julian Assange's legal future last night as the WikiLeaks founder agreed to meet British police to discuss allegations of sexual assault against him in Sweden. Assange was not arrested last night, but that remains a possibility after the Serious Organised Crime Agency (Soca) received a European arrest warrant (EAW) from Sweden.

Assange's lawyers said he had not been formally charged in Sweden, where he faces the sex allegations. But under the EAW system, a warrant can only be issued once a charge has been made.

Assange is wanted for questioning by Swedish officials, and could consent to return there to co-operate with their investigation. While the EAW's legal status is uncertain, once validated by British authorities Assange's arrest would be inevitable and he would have to brought before a magistrate "as soon as practicable", or in most cases within 24 hours. If arrested Assange will appear before Westminster magistrates.

A key issue will be whether Assange is released on bail during that period. His lawyers are reported to be putting together a generous package, including a security of at least £100,000 and a surety – where third parties guarantee to pay the court if he absconds. However, the allegations facing Assange are serious in Swedish law and it is often more difficult to secure bail for these.

Assange's lawyers are disputing the credibility of the allegations and the motive behind Sweden's decision to investigate the matter further, after prosecutors dropped it earlier this year, and are likely to challenge the grounds for extradition.

But if extradited to Sweden under the EAW, Assange will be vulnerable to other extradition requests from countries including the US. The US has an extradition treaty with Sweden dating back to 1960s, when the two countries agreed to "make more effective the cooperation of the two countries in the repression of crime." Extradition under the treaty is likely to face a number of obstacles, not least the fact that the likely charges facing Assange in the US – under the Espionage Act or other legislation protecting national security – are not included in the exhaustive list of offences set out in the law. There may also be issues of jurisdiction, since the offences which Assange is accused of did not take place in the US.Even if Assange's case falls outside the scope of Sweden's treaty with the US, there would still be scope for the country to agree to his extradition to the US.

Swedish law permits extradition more generally to countries outside Europe, although the process is subject to safeguards, including a ban on extradition for "political offences" or where the suspect has reason to fear persecution on account of their membership of a social group or political beliefs.

Any extradition from Sweden to the US could only take place after the current proceedings were concluded. With Assange's lawyers intending to dispute those proceedings on all grounds, it seems the prospect of any extradition to the US remains some way away.